MySQL 8.0 Reference Manual Including MySQL NDB Cluster 8.0
The Performance Schema table described here is available as
of MySQL 8.0.14. Prior to MySQL 8.0.14, use the
corresponding INFORMATION_SCHEMA table
instead; see
Section 26.52.2, “The INFORMATION_SCHEMA TP_THREAD_GROUP_STATS Table”.
The tp_thread_group_stats table
reports statistics per thread group. There is one row per
group.
The tp_thread_group_stats table
has these columns:
TP_GROUP_ID
The thread group ID. This is a unique key within the table.
CONNECTIONS_STARTED
The number of connections started.
CONNECTIONS_CLOSED
The number of connections closed.
QUERIES_EXECUTED
The number of statements executed. This number is incremented when a statement starts executing, not when it finishes.
QUERIES_QUEUED
The number of statements received that were queued for execution. This does not count statements that the thread group was able to begin executing immediately without queuing, which can happen under the conditions described in Section 5.6.3.3, “Thread Pool Operation”.
THREADS_STARTED
The number of threads started.
PRIO_KICKUPS
The number of statements that have been moved from
low-priority queue to high-priority queue based on the
value of the
thread_pool_prio_kickup_timer
system variable. If this number increases quickly,
consider increasing the value of that variable. A quickly
increasing counter means that the priority system is not
keeping transactions from starting too early. For
InnoDB, this most likely
means deteriorating performance due to too many concurrent
transactions..
STALLED_QUERIES_EXECUTED
The number of statements that have become defined as
stalled due to executing for longer than the value of the
thread_pool_stall_limit
system variable.
BECOME_CONSUMER_THREAD
The number of times thread have been assigned the consumer thread role.
BECOME_RESERVE_THREAD
The number of times threads have been assigned the reserve thread role.
BECOME_WAITING_THREAD
The number of times threads have been assigned the waiter thread role. When statements are queued, this happens very often, even in normal operation, so rapid increases in this value are normal in the case of a highly loaded system where statements are queued up.
WAKE_THREAD_STALL_CHECKER
The number of times the stall check thread decided to wake or create a thread to possibly handle some statements or take care of the waiter thread role.
SLEEP_WAITS
The number of THD_WAIT_SLEEP waits.
These occur when threads go to sleep (for example, by
calling the SLEEP()
function).
DISK_IO_WAITS
The number of THD_WAIT_DISKIO waits.
These occur when threads perform disk I/O that is likely
to not hit the file system cache. Such waits occur when
the buffer pool reads and writes data to disk, not for
normal reads from and writes to files.
ROW_LOCK_WAITS
The number of THD_WAIT_ROW_LOCK waits
for release of a row lock by another transaction.
GLOBAL_LOCK_WAITS
The number of THD_WAIT_GLOBAL_LOCK
waits for a global lock to be released.
META_DATA_LOCK_WAITS
The number of THD_WAIT_META_DATA_LOCK
waits for a metadata lock to be released.
TABLE_LOCK_WAITS
The number of THD_WAIT_TABLE_LOCK waits
for a table to be unlocked that the statement needs to
access.
USER_LOCK_WAITS
The number of THD_WAIT_USER_LOCK waits
for a special lock constructed by the user thread.
BINLOG_WAITS
The number of THD_WAIT_BINLOG_WAITS
waits for the binary log to become free.
GROUP_COMMIT_WAITS
The number of THD_WAIT_GROUP_COMMIT
waits. These occur when a group commit must wait for the
other parties to complete their part of a transaction.
FSYNC_WAITS
The number of THD_WAIT_SYNC waits for a
file sync operation.
The tp_thread_group_stats table
has these indexes:
Unique index on (TP_GROUP_ID)
TRUNCATE TABLE is not permitted
for the tp_thread_group_stats
table.